Kristine M. Graham

Characterization and Control of Organic Airborne Contamination in Lithographic Processing

In the DUV lithographic process, airborne contamination, such as ammonia and 1-methyl-2-pyrrolidinone, is known to present several processing problems. Presently, these airborne contaminants are effectively controlled using either acid-base or ion-exchange chemistry. However, as lithographic processing moves towards the creation of smaller features using 193 nm and 157 nm technologies, airborne and condensable organic contamination presents an ever-increasing concern. In addition, the wide range of chemical and physical properties of the organic contaminants found in the processing environment, do not lend themselves to effective control using the specific chemisorptive techniques currently applied. In conjunction with our efforts to design improved chemical filters for the effective control of organic airborne contaminants, we have attempted to characterize the organic airborne contamination found in the lithographic processing environment. In addition, we have evaluated the effectiveness of activated carbon filters for their removal. In this report, we will present our current findings and reveal some of the benefits and concerns associated with the use of activated carbon-based chemical filters for the control of organic airborne contamination in present and future processing applications.

Protecting the DUV process and optimizing optical transmission

It has been well documented that DUV lithographic processes are sensitive to airborne contamination such as ammonia and n- methyl-2-pyrrolidone (NMP). Chemical filtration technologies have aided in minimizing the problems associated with these contaminants in the photolithographic process. As the demand for smaller features increases, so will the need to operate within even cleaner environments than are available today. One such area where airborne contamination has proven to be of significant concern, is within the lensing system of the tool. With decreasing feature size, the lithographic process has proven to be more sensitive to contamination of the lens itself, and within the environment surrounding the lens. Condensation on the lens (hazing) and the presence of contamination between the lens and substrate can result in poor optical transmission. To minimize these problems, a purge gas is typically employed. Even though high purity gases are used, contamination within the gas still is an issue. This work describes our efforts directed at understanding the purge gas and lens environments. In addition, we will address our efforts that have focused on the development of chemical filters that provide environments for optimized optical transmission in lithographic applications.

Advancements in Electrospun Nanofiber Technology Reduce Gas Turbine Compressor Fouling

It is well established that sub-micron ambient aerosol contamination of the intake air can produce fouling of the gas turbine compressor and result in a reduction of power output. Application of electrospun nanofibers of 0.25 micron diameter to a conventional filter media substrate has been demonstrated to improve the efficiency of gas turbine intake filters to remove sub-micron contaminate. The benefits of nanofiber filtration have been proven through use in gas turbine intake air filtration and other industrial and defense filtration applications for over twenty years. Recent advancements in electrospun nanofiber media technology have increased the filtering efficiency of gas turbine intake filters, with minimal differences in filter element pressure loss. These advances have also improved the durability of nanofibers in high temperature and high humidity applications. This paper discusses the laboratory testing that demonstrates these performance and durability improvements. A comparative field test program demonstrates the capability of nanofiber filtration to significantly reduce the fouling of gas turbine compressors.Copyright